EXPERIMENTAL CHARACTERISATION OF AN OSCILLATING REACTING SHEAR LAYER
Edgar C. Fernandes
Mechanical Engineering Department Instituto Superior Tecnico Av. Rovisco Pais, 1049-001 Lisboa Codex Portugal
Manuel V. Heitor
Instituto Superior Técnico, Technical University of Lisbon, Department of Mechanical Engineering, Av. Rovisco Pais, 1096 Lisboa, Codex, Portugal
An unsteady propane-air premixed flame stabilised in a bluff-body is investigated, in particular the reacting shear layer close to the burner base bounded by central recirculation zone, with hot products, and non-reacting vortex shedding. The flow field oscillates with frequency of 275Hz and the unsteady process is driven by an acoustic standing half-wave accommodated inside the upstream pipe. Optical and probe techniques, such as laser velocimetry, digitally-compensated thermocouples, chemiluminiscent sensor for 2*> emission and a microphone, were used for the analysis of the coupling mechanisms between pressure, velocity and heat release fluctuations typical of pulsed flames. Phase locked results show that the unsteady reacting shear layer features strong temporal and spatial deformations where the relation between turbulent and mean field can be modelled based on the gradient hypothesis, except in the presence of the vortex.